Fabric sheet with hig thermal stability

ABSTRACT

A fabric sheet, with low-cost production, has high thermal and light stability, is recyclable, has a high mechanical load-bearing capacity, and is elastically compliant, wherein the fabric sheet has a main body composed of at least one ply, wherein the at least one ply contains first fibers comprising a first polymer and second fibers with a second polymer or wherein the at least one ply has one and the same fibers that contain a first and a second polymer, wherein a cold crystallization temperature of the first polymer lies at the softening temperature of the second polymer or below the softening temperature of the second polymer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. national stage application under 35 U.S.C. §371 of International Application No. PCT/EP2014/002469, filed on Sep. 12, 2014, and claims benefit to German Patent Application No. DE 10 2013 016 293.9, filed on Oct. 2, 2013. The International application was published in German on Apr. 9, 2015, as WO 2015/049027 A1 under PCT Article 21(2).

FIELD

The invention relates to a sheet product, preferably of high thermal stability, and also to its use in the manufacture of a component part for a means of transport.

BACKGROUND

Sheet products of the type referred to at the beginning are already known from the prior art and are used in many fields, for example in the transportation industry. Sheet products of this type typically contain a very wide variety of materials, for example glass fibers, polyurethanes or polyesters.

U.S. Pat. No. 3,966,526 describes a method of making component parts for automotive interior trim. They are constructed of multiple foam-type layers comprising polystyrene resin. The disadvantage here is that these component parts are not recyclable and their disposal is accordingly associated with high costs.

A further component part for the automotive industry, namely a headliner, is shown in U.S. Pat. No. 4,840,832. The headliner comprises bicomponent fibers of polyester having a low-melting binder component and a high-melting stabilizing polymer.

U.S. Pat. No. 5,275,865 discloses a further headliner for automotive interior trim, this headliner containing partially oriented polyester fibers and no binder.

U.S. Pat. No. 4,119,749 describes a lightweight headliner for automotive interior trim. It has a multilayered construction. A layer of polyurethane foam is employed as core element in that one side of the polyurethane foam layer is provided a further polyurethane foam layer. The other side is impregnated with an elastomer solution. The individual layers need to be separated to dispose of the headliner. This increases the costs of disposal. Recycling of the foams is also not possible owing to the selected materials.

U.S. Pat. No. 4,211,590 shows a thermoformable laminate comprising a thermoplastic foam-type core. After thermoforming, the laminate is rigidified by cooling. A laminate of this type is used for trimming the interior of an automobile, particularly as a headliner.

A further headliner for automotive interior trim is known from U.S. Pat. No. 5,660,908. It consists of polyethylene terephthalate and has reinforcing ribs. The disadvantage here is its lack of thermal stability. Adequate thermal stability is achievable through a complicated construction. This requires a costly and inconvenient method of making.

Sheet products of the type referred to at the beginning typically have a low level of flexural stiffness at elevated temperature, are not recyclable or have a high level of stiffness coupled with low elasticity/formability. This compromises the processing of such a sheet product; especially the processing of such a sheet product into interior trim for an automobile, is associated with appreciable difficulties. The achievement of adequate stability while retaining the elasticity of the sheet product requires a multilayered structural design. This in turn requires a costly and inconvenient method of making.

SUMMARY

An aspect of the invention provides a sheet product, comprising: a main body comprising a ply, wherein the ply comprises first fibers comprising a first polymer and second fibers comprising a second polymer or wherein the ply comprises unitary fibers comprising first and second polymers, wherein a cold crystallization temperature of the first polymer is equal to the softening temperature of the second polymer or below the softening temperature of the second polymer.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described in even greater detail below based on the exemplary figures. The invention is not limited to the exemplary embodiments. All features described and/or illustrated herein can be used alone or combined in different combinations in embodiments of the invention. The features and advantages of various embodiments of the present invention will become apparent by reading the following detailed description with reference to the attached drawings which illustrate the following:

FIG. 1 shows a sheet product comprising a main body of one ply, said ply containing fibers from two polymers;

FIG. 2 shows a schematic arrangement of a thermoformable sheet product;

FIG. 3 shows a further schematic arrangement of a thermoformable sheet product;

FIG. 4 shows a schematic arrangement of a two-ply thermoformable sheet product;

FIG. 5 shows a diagram comparing the heating curve of the first polymer with the second polymer;

FIG. 6a shows a trilobal fiber in cross section;

FIG. 6b shows a further trilobal fiber in cross section; and

FIGS. 7a-c show optical micrographs of cross sections through three bicomponent fibers.

DETAILED DESCRIPTION

An aspect of the invention therefore addresses the problem of refining and developing a sheet product of the type referred to at the beginning such that it, following inexpensive fabrication, has a high level of flexural stiffness at elevated temperature, and is recyclable, mechanically strong and elastically resilient. This sheet product shall find use in particular as a component part for a means of transport.

In an aspect, the sheet product referred to at the beginning accordingly comprises a main body of at least one ply, wherein the at least one ply contains first fibers comprising a first polymer and second fibers comprising a second polymer or wherein the at least one ply comprises unitary fibers containing first and second polymers, wherein a cold crystallization temperature of the first polymer is equal to the softening temperature of the second polymer or below the softening temperature of the second polymer.

Cold crystallization is to be understood as meaning a crystallization occurring after heating beyond the softening and/or glass transition temperature.

Cold crystallization temperature is to be understood as meaning the temperature at which a first exothermic maximum of the free enthalpy occurs. Exothermic is to be understood as meaning a release of energy.

Softening temperature, also known as glass transition temperature, is to be understood as meaning the temperature at which wholly or partly amorphous polymers transition from a highly viscous or rubberily elastic, flexible state into a glass-type or hard elastic state. Softening temperature in this invention is measured to DIN 53765.

By unitary fibers is meant that the fibers have the same polymers and the same fiber type.

The inventors recognized that the cold crystallization of the first polymer causes a stabilization of the second polymer to occur at the softening temperature of the second polymer or below the softening temperature of the second polymer. This results in a sheet product having sufficiently high mechanical strength at high temperatures. The sheet product is further notable for outstanding acoustical properties and a low weight.

The problem referred to at the beginning has accordingly been solved.

Preferably, a cold crystallization of the first polymer occurs at a softening temperature of the second polymer in the range from 70 to 150° C., preferably in the range from 80 to 140° C., more preferably in the range from 90 to 130° C. These conditions result in a sheet product having high flexibility and elastic yieldingness at high temperatures.

At these temperatures, a stabilization of the second polymer takes place due to crystallization of the first polymer.

Preferably, there is no difference between the cold crystallization temperature of the first polymer and the softening temperature of the second polymer. However, the difference between the cold crystallization temperature of the first polymer and the softening temperature of the second polymer could also be in the range from 1 to 100° C., preferably in the range from 2 to 80° C., more preferably in the range from 3 to 60° C. These conditions result in particularly good stabilization of the second polymer due to cold crystallization of the first polymer.

In one preferred embodiment, the softening temperature and/or the melting temperature of the second polymer are/is above the softening temperature and/or the melting temperature of the first polymer. Specific selection of the polymers with regard to their softening temperatures and also their melting temperatures ensures particularly good stabilization of the first polymer due to the second polymer up to the softening temperature of the second polymer. The specific selection of the polymers and their arrangement due to the cold crystallization of the first polymer further endow the sheet product with a level of thermal stability that is distinctly above the softening temperature and the melting temperature of either polymer.

The difference between the softening temperatures as measured to DIN 53765 for the first and second polymers can vary within wide limits. Advantageously, the difference in the softening temperatures of the first and second polymers is at least 15° C., preferably at least 20° C., more preferably at least 25° C. Preference is given to employing polymers having a temperature difference of from 15 to 450° C., more preferably from 20 to 150° C., yet more preferably from 25 to 100° C. Practical tests have shown that these values provide a particularly high level of thermal stability to the sheet product.

In one preferred embodiment, the difference between the melting temperatures of the first and second polymers is at least 5° C., preferably at least 10° C., more preferably at least 15° C. Preference is given to using polymers having a temperature difference of from 5 to 200° C., more preferably of from 10 to 150° C., yet more preferably from 15 to 120° C. This difference in the melting temperatures of the two polymers leads to good thermal stability and to good load-deflection characteristics for the sheet product.

A very wide variety of materials are employable as polymers. Preferably, the polymers are melt spinnable. Preferably, at least one of the polymers is a polyester selected from the group consisting of polyethylene terephthalate, polypropylene terephthalate, polytetramethylene terephthalate, poly(decamethylene) terephthalate, poly-1,4-cyclo-hexylene dimethyl terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyglycolic acid, polylactides, polycaprolactones, polyethylene adipates, polyhydroxyalkanoates, polyhydroxybutyrates, poly-3-hydroxybutyrate-co-3-hydroxyvalerates, poly-trimethylene terephthalates, vectrans, polyethylene naphthalate, their copolymers and/or their mixtures. Sheet products comprising the aforementioned polymers are readily recyclable.

It is extremely preferable for the first polymer to be selected from the group consisting of polypropylene terephthalate, polytetramethylene terephthalate, poly(decamethylene) terephthalate, poly-1,4-cyclo-hexylene dimethyl terephthalate, polybutylene terephthalate, polyethylene terephthalate, more preferably polypropylene terephthalate, polytetra-methylene terephthalate, polyethylene terephthalate, their copolymers and/or their mixtures.

It is further extremely preferable for the second polymer to be selected from the group consisting of poly(decamethylene)terephthalate, poly-1,4-cyclo-hexylene dimethyl terephthalate, polybutylene terephthalate, polyethylene naphthalate, more preferably polyethylene naphthalate, polybutylene terephthalate, their copolymers and/or their mixtures. A suitable choice of the polymers used can be used to influence the thermal stability and also the mechanical properties, in particular the elasticity, formability and strength of the sheet product. This enables custom-tailoring of the sheet product to various applications, preferably to applications of the sheet product as a substrate for interior trimming of means of transport and as a cladding material for the outside.

It is very particularly preferable for the first polymer to be a polyester selected from the group consisting of polyglycolic acid, polylactides, polycaprolactones, polyethylene adipates, polyhydroxy-alkanoates, polyhydroxybutyrates, poly-3-hydroxy-butyrate-co-3-hydroxyvalerates, polyethylene terephthalate, polypropylene terephthalate, poly-butylene terephthalate, polytrimethylene terephthalates, vectrans, polytetramethylene terephthalate, poly(decamethylene) terephthalate, poly-1,4-cyclohexylene dimethyl terephthalate, polyethylene naphthalate, their copolymers and/or their mixtures and for the second polymer to contain polyethylene naphthalate.

In a preferred embodiment, the first polymer contains polyethylene terephthalate and/or co-polyethylene terephthalate and the second polymer contains polyethylene naphthalate.

Preferably, the first polymer has a cold crystallization temperature in the range from 70 to 150° C., more preferably in the range from 80 to 140° C., most preferably in the range from 90 to 130° C. These polymers have a high level of thermal stability and lead to good load-deflection characteristics for the sheet product.

In a further preferred embodiment, the second polymer has a softening temperature in the range from 70 to 150° C., more preferably in the range from 80 to 140° C., most preferably in the range from 90 to 130° C. This results in particularly good stabilization of the second polymer through cold crystallization of the first polymer.

Practical tests have shown that particularly high stiffnesses are achieved when the first polymer has a lower modulus of elasticity than the second polymer. The modulus of elasticity is a physical parameter from the science of engineering materials, and describes the relationship between stress and strain as a solid body undergoes deformation in the linear elastic region. The first polymer could have a modulus of elasticity in the range from 400 to 1300 MPa, preferably in the range from 500 to 1200 MPa, more preferably in the range from 700 to 1000 MPa.

The second polymer could have a high modulus of elasticity. The second polymer preferably has a modulus of elasticity in the range from 1400 to 3000 MPa, more preferably in the range from 1600 to 2500 MPa, yet more preferably in the range from 2000 to 2200 MPa. This provides an outstanding level of flexural stiffness at elevated temperature.

Preferably, at least one fiber contains at least two polymers, wherein the first polymer is in the form of at least one segment embedded in the second polymer and/or at least partly bordered by the second polymer. This causes the second polymer to stabilize the first polymer under high temperatures until the first polymer undergoes cold crystallization.

Advantageously, segments of a first polymer are present in the sheet product in a circular, oval or n-angular, trilobal or multilobal cross section and embedded in the second polymer and/or at least partly bordered by the second polymer. The alternating arrangement of the individual segments results in an optimal and uniform arrangement of the first polymer in the form of segments embedded in the second polymer and/or at least partly bordered by the second polymer. Round segments are preferable and their coaxial arrangement is particularly preferable. Force absorption is good as a result of this isotropic arrangement.

The fibers could have a sheath-core geometry. In a sheath-core geometry, the first polymer in the core of a filamentary strand is surrounded by the second polymer. Preferably, the core contains polypropylene terephthalate, polytetramethylene terephthalate, poly(decamethylene) terephthalate, poly-1,4-cyclo-hexylene dimethyl terephthalate, polybutylene terephthalate, polyethylene terephthalate, more preferably polypropylene terephthalate, polytetra-methylene terephthalate, polyethylene terephthalate, their copolymers and/or their mixtures and the sheath contains with preference poly(decamethylene) terephthalate, poly-1,4-cyclohexylene dimethyl terephthalate, polybutylene terephthalate, polyethylene naphthalate, more preferably polyethylene naphthalate, polybutylene terephthalate, their copolymers and/or their mixtures. In these geometries, the first polymer is advantageously embedded in the second polymer in a particularly homogeneous manner, and these geometries lead to a particularly dense structure.

The fibers are advantageously embodied as monofibers. It is advantageous in this connection for the second polymer to be adhered to the first polymer and for the first polymer to act as a binder fiber and create an adhesive bond between the fibers of the first and second polymers. This serves to enhance the mechanical strength of the sheet product.

In a further preferred embodiment, the fibers have a sheath-core geometry where the fibers contain just one polymer. There is preferably no polymer in the core. Hollow fibers are concerned in this case. This is advantageous in providing a sheet product of low weight and high mechanical strength.

It is further preferable for the polymer of the hollow fiber to be a polyester selected from the group consisting of polypropylene terephthalate, polytetramethylene terephthalate, poly(decamethylene) terephthalate, poly-1,4-cyclohexylene dimethyl terephthalate, polybutylene terephthalate, polyethylene terephthalate, polypropylene terephthalate, polytetramethylene terephthalate, polyethylene terephthalate, polyethylene naphthalate, their copolymers and/or their mixtures. It is extremely preferable for the polymer of the hollow fiber to contain polyethylene naphthalate.

It is extremely preferable for the polymer of the hollow fiber to have a softening temperature in the range from 70 to 150° C., more preferably in the range from 80 to 140° C., extremely preferably in the range from 90 to 130° C. This provides a particularly stable sheet product of low weight.

In a preferred embodiment, the weight ratio of the first to the second polymer is in a range from 50:50 to 95:5, preferably in a range from 60:40 to 95:5, more preferably in a range from 65:35 to 90:10. Advantageously, even a small fraction of the polymer having the higher softening and/or melting temperature is sufficient to obtain optimal stabilization of the polymer having the lower softening and/or melting temperature. It is further possible to reduce manufacturing costs by having a low proportion of the second polymer, since it is typically the costlier component.

Fiber diameter is preferably in the range from 0.1 to 20 dtex, more preferably in the range from 1 to 15 dtex, yet more preferably in the range from 3 to 12 dtex. It is particularly preferred to employ the second polymer as the minority component. The advantage with this is that the typically costly second polymeric component can be employed in a material-saving manner to enhance the stability of the sheet product.

The stability of the sheet product can further be additionally enhanced by using a first polymer to partly or wholly fill the voids between the fibers.

In a preferred embodiment, the main body does not contain any further fibers. Conceivably, the main body could include further fibers. These fibers are preferably embodied as monofibers. The proportion of further fibers in relation to the overall weight of the main body is preferably in the range from 1 to 80 wt %, preferably from 10 to 70 wt %, more preferably from 20 to 60 wt %.

In a preferred embodiment, the further fibers contain a polymer selected from the group consisting of polyesters, polyolefins, polyamide, nylon 66 (Nylon®), nylon 6 (Perlon® preferably polyethylene terephthalate, polypropylene terephthalate, their copolymers and/or their mixtures.

The fibers may be embodied as binder fibers. The binder fiber creates an adhesive bond serving to enhance the strength of the sheet product.

The plies, preferably the at least one ply and/or the further plies of the main body, could be embodied as a non-crimp fabric, as a woven fabric, as a knit fabric, as a film, as a foil, as a batt or as a nonwoven. A sheet product having mechanical strength is obtained as a result.

The main body could include a composite material which contains the at least one ply. The mechanical strength of the sheet product is enhanced as a result.

It is conceivable for the sheet product to include a reinforcing ply. Preferably, the sheet product does not include any reinforcing ply. This provides a sheet product of high mechanical strength and low weight.

Against this background it is also conceivable to subject the sheet product to a chemical type of finish or treatment, for example—if needed or desired—a hydrophilicization, an antistatic treatment, a treatment to improve the fire resistance or the light stability and/or to modify the tactile properties or the luster, and/or a treatment to modify the appearance such as dyeing or printing.

Basis weight may vary between wide limits. The sheet product preferably has a basis weight as measured to DIN EN 29073 1 in the range from 50 to 4000 g/m², preferably in the range from 80 to 3000 g/m², more preferably in the range from 100 to 2500 g/m². Sheet products having the aforementioned basis weights possess outstanding stability.

In a preferred embodiment, the sheet product is used as a headliner substrate. In this use, the sheet product preferably has a basis weight in the range from 500 to 2500 g/m², more preferably in the range from 100 to 1000 g/m², extremely preferably in the range from 200 to 800 g/m².

In a preferred embodiment, the sheet product has a DIN EN 9073 2 thickness of from 0.5 to 300 mm, more preferably from 1 to 200 mm, yet more preferably from 1 to 150 mm. Sheet products of this type have particularly good processing properties by virtue of their low thickness and good formability.

The present invention further provides a bicomponent fiber containing first and second polymers, wherein a cold crystallization temperature of the first polymer is equal to the softening temperature of the second polymer or below the softening temperature of the second polymer.

In a preferred embodiment, the sheet product is subjected to a thermoforming operation to obtain a thermoformed sheet product. Thermoforming is a forming operation practiced on thermoplastic materials. The thermoformed sheet product could be obtainable by a process comprising the steps of:

a) heating the sheet product,

b) introducing the sheet product into a mold,

c) compression molding in the mold, and

d) removing the sheet product from the mold.

The mold could be heated to a temperature in the range from 20 to 300° C., preferably in the range from 20 to 250° C. The mold advantageously has two halves. The two halves of the mold may be spaced apart the same or differently at various points of the compression-molding surface during the compression-molding step. Practical tests have shown that under these conditions the thermoformable sheet product is endowed with an enhanced level of flexural stiffness at elevated temperature.

The flexural stiffness of the sheet product may vary between wide limits. The sheet product is preferably used in the manufacture of a component part for a means of transport, in particular as a substrate for a headliner. Sheet products of this type preferably have a flexural stiffness in the range from 1 to 40 N/mm² as measured to DIN EN ISO 14125 at a maximal flexural stress, more preferably in the range from 1 to 25 N/mm², yet more preferably in the range from 2 to 20 N/mm², extremely preferably in the range from 4 to 15 N/mm². Sheet products having the aforementioned flexural stiffnesses combine outstanding formability with sufficient stability.

The flexural stiffness of the thermoformed sheet product can also be determined according to DIN/EN 310. On setting the test speed to 20 mm/min, the sample size to 90 mm×75 mm, the support point separation to 80 mm and the initial force to 3 N, it is possible to obtain flexural stiffnesses in the range from 1 to 40 N, preferably from 5 to 35 N and particularly from 10 to 30 N. The thermoformed sheet product embodied as substrate for a headliner could further have a modulus of elasticity (E-modulus) in the range from 20 to 350 MPa as measured to EN ISO 14125 at a maximal flexural stress, preferably in the range from 30 to 280 MPa, more preferably in the range from 40 to 250 MPa. The modulus of elasticity is a physical parameter from the science of engineering materials, and describes the relationship between stress and strain as a solid body undergoes deformation in the linear elastic region.

The modulus of elasticity of the thermoformed sheet product can also be determined according to DIN EN ISO 178. On setting the test speed to 20 mm/min, the sample size to 90 mm×75 mm, the support point separation to 80 mm and the initial force to 3 N, it is possible to obtain moduli of elasticity in the range 20 to 600 MPa, preferably from 30 to 500 MPa and particularly from 40 to 450 MPa.

In a further preferred embodiment, the sheet product embodied as substrate for a headliner has a modulus of elasticity (E-modulus) in the range from 10 to 350 MPa as measured to EN ISO 14125 or to DIN EN ISO 178 at a maximal flexural stress and a temperature of 120° C., preferably in the range from 15 to 250 MPa, more preferably in the range from 20 to 200 MPa. It is advantageous here that the sheet product possesses an enhanced level of mechanical strength at high temperatures. Aging processes preferentially proceed very slowly, so the sheet product stands up even to the high requirements which component parts are expected to meet in the automotive industry. A surface, for example, must not exhibit any color change or scarring after several months of photoaging at 120° C.

In a preferred embodiment, the sheet product has a multi-ply construction. Preferably, the sheet product contains further plies in addition to the main body. The further plies could be embodied as spunbond plies or as a staple fiber ply. The further plies differ from each other in their function, method of making, fiber type, containing polymers and/or in their color. A combination of staple fiber ply and spunbond ply leads to a voluminous sheet product for the same basis weight. The sheet product could further have further plies embodied as spunbond or staple fiber ply. This improves the acoustical properties.

In a further preferred embodiment, the thermoformed sheet product comprises a sandwich structure wherein the outer plies contain the sheet product of the present invention. The central ply could comprise a staple fiber ply or a further spunbond ply. Advantageously, the sandwich-type construction enhances the flexural stiffness and endows the sheet product with excellent strength. The following further sequences are considerable. Hereinbelow SF represents a staple fiber ply and SL represents a spunbond ply: SF/SL/SF; SF/SL; SL/SF.

These sequences could also be combined with plies as described above.

The sheet product of the present invention has high flexural stiffness at elevated temperature, a low weight and sound absorption and therefore is useful in the manufacture of a component part for a means of transport. The sheet product is very useful as a substrate for the interior fitment of a means of transport, more preferably as a substrate for a headliner, as a substrate for an internal door trim panel, as a substrate for a parcel shelf and/or as a substrate in the exterior region of a means of transport, more preferably as a substrate for an underbody and as a substrate for a wheel box. Means of transport is to be understood as referring to automobiles, trucks, coaches, rail cars, airplanes, ships, recreational vehicles, agricultural machines and/or campers.

In one preferred embodiment, the sheet product is used as a substrate for interior trim paneling of a coach, of a camper, of a recreational vehicle, of a ship, of an airplane or of a rail vehicle. The sheet product is suitable for the aforementioned uses by virtue of its mechanical strength and its low weight.

It is further conceivable to use the sheet product as a substrate for an interior fitting-out of ships' cabins and/or airplane cabins because of its low weight.

The sheet product could further be used in the manufacture of a component part for a building, preferably as a substrate for mobile dividing walls or partitions in buildings. This use rests on the low weight of the sheet product and its outstanding acoustical properties.

The invention will now be more particularly described with reference to a number of examples which do not limit the invention.

Example 1 Making an Inventive Sheet Product

PEN pellet (Advanite 71001 from SASA) and copolyester pellet (CS 123 N from FENC) material is dried and subsequently melt spun into a mixture of monofibers and bicomponent fibers.

The processing temperature is 300° C. for Advanite and 270° C. for CS 123 N.

The spinneret die used is a 195 hole die having a bicomponent fiber fraction of 60%. The PEN is exclusively imported into the sheath of the bicomponent fiber, the copolyester not only into the core of the bicomponent fiber but also into the monofiber.

Three different ratios of PEN/copolyester are created in the bicomponent fiber.

1. 30% PEN (sheath) 70% copolyester (core)

2. 25% PEN (sheath) 85% copolyester (core)

3. 20% PEN (sheath) 80% copolyester (core)

Optical micrographs of cross sections through the above bicomponent fibers 1-3 are shown in FIGS. 7a -c.

Example 2 Determining Relevant Fiber Parameters

Some relevant fiber properties are determined on the spun bicomponent fibers as follows:

fineness: 8.5 dtex

tenacity: 21.54 cN/tex

elongation: 10.19%

boil shrinkage: 3.25%

In addition, thermal stability under temperature forcing was tested as follows:

A bicomponent fiber 8 cm in length was stretched between two metal blocks 4 cm apart and loaded with a weight of 1 g in the center. The fiber was taut.

The temperature was then raised to 100° C., which is above the Tg of the copolyester used and below the Tg of the PEN. No sagging was observed for the bicomponent fiber. Next the temperature was raised to 125° C., this temperature being within the softening range of the PEN. Again no sagging was observed. Finally, the temperature was raised to 140° C. This temperature is above the softening range of the polyester. Merely minimal sagging was observed at this temperature.

Since the copolyester already softens in a range of 55 65° C., a standard polyester monofiber (PET) was used as reference. The test performed has shown that distinct sagging of the PET monofiber is observed on reaching just 100° C.

Example 3 Production of Multi-Ply Hybrid Materials

The spunbond made in Example 1 was combined with a staple fiber ply as a reinforcing ply consisting of bicomponent fibers (LMF50 from Huvis, PET/CoPET, 4.4 dtex, 64 mm) to produce not only two-ply but also three-ply hybrid materials.

To this end, either one or two spunbonds were combined with one staple fiber ply by means of a needle loom. In the three-ply hybrid materials, the staple fiber batt was in each case placed in the center.

Six different hybrid materials were made using the following settings for the needle loom:

frequency 1000 min⁻¹ penetration 10 mm speed 4 m needle board 15 × 18 × 40 × 3.5 (Singer)

Hybrid Materials Obtained

number of plies basis weight 2 410 g/m² 2 480 g/m² 2 530 g/m² 2 640 g/m² 3 470 g/m² 3 510 g/m²

Following needling, the hybrid materials were consolidated using a belt dryer. Belt dryer setting:

speed 1 m temp. of chamber 1 230° C. temp. of chamber 2 230° C. 1 air recycled 100% 2 air recycled 100% 1 nozzle adjustment 1.5 cm 2 nozzle adjustment 1.5 cm air exhausted  80%

Consolidated Hybrid Materials Obtained

number of basis mass mass plies weight increase/g increase/% 2 440 g/m² 30 7.3 2 520 g/m² 40 8.3 2 580 g/m² 50 9.4 2 700 g/m² 60 8.6 3 510 g/m² 40 8.5 3 560 g/m² 50 9.8

Test specimens 90 mm×75 mm in size were die-cut out of the hybrid materials obtained and compression molded at a temperature of 180° C. down to a thickness of 2.1 2.5 mm, followed by the determination of the bending force to DIN/EN 310 at an initial force of 3 N and a test speed of 20 mm, the E-modulus to DIN EN ISO 178 at the same initial force and test speed.

basis E-modulus/ bending path/ weight MPa force/N mm 440 g/m² 105 4.7 4.4 520 g/m² 136 6.4 8.1 580 g/m² 171 7.9 10.2 700 g/m² 232 16.3 12.5 510 g/m² 151 6.5 8.3 560 g/m² 142 7.7 9.6

FIG. 1 shows a sheet product 1 comprising a main body of one ply 2, said ply 2 containing fibers from two polymers.

Ply 2 has a single-ply construction.

FIG. 2 shows a schematic arrangement of a thermo-formable sheet product 1′. The sheet product 1′ has a multi-ply construction in that it contains further plies besides ply 2. Ply 2 is embodied as a spunbond ply. The sheet body 1′ includes a ply 3 of staple fibers as the bottommost layer. A ply 2 is arranged atop this ply 3. A further ply 3 of staple fibers is positioned atop ply 2.

FIG. 3 shows a further schematic arrangement of a thermoformable sheet product 1″. The sheet product 1″ has a multi-ply construction in that it contains further plies besides ply 2. The sheet product 1″ includes ply 2 as the bottommost layer. A ply 3 of staple fibers is arranged atop this ply 2. A further ply 2 is positioned atop ply 3 of staple fibers.

FIG. 4 shows yet a further schematic arrangement of a thermoformable two-ply sheet product 1′″. The sheet product 1′″ includes ply 2 as bottommost layer. A staple fiber ply 3 is arranged atop this ply 2.

FIG. 5 shows a diagram comparing the heating curve of the first polymer with the second polymer according to the temperature.

The upper curve 4 shows the heating behavior of the first polymer and the lower curve 5 describes the heating behavior of the second polymer. The softening temperature 6 of the first polymer is below the softening temperature 7 of the second polymer.

The cold crystallization temperature 8 of the first polymer is below the softening temperature 7 of the second polymer. The cold crystallization temperature 9 of the second polymer is above the cold crystallization temperature 8 of the first polymer.

FIG. 6a shows a cross section through a trilobal fiber containing two polymers, the first polymer 10 being in the form of at least one segment embedded in a second polymer 11.

FIG. 6b shows a cross section through a trilobal fiber containing two polymers, the first polymer 10 being in the form of at least one segment at least partly bordered by the second polymer 11.

While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. It will be understood that changes and modifications may be made by those of ordinary skill within the scope of the following claims. In particular, the present invention covers further embodiments with any combination of features from different embodiments described above and below. Additionally, statements made herein characterizing the invention refer to an embodiment of the invention and not necessarily all embodiments.

The terms used in the claims should be construed to have the broadest reasonable interpretation consistent with the foregoing description. For example, the use of the article “a” or “the” in introducing an element should not be interpreted as being exclusive of a plurality of elements. Likewise, the recitation of “or” should be interpreted as being inclusive, such that the recitation of “A or B” is not exclusive of “A and B,” unless it is clear from the context or the foregoing description that only one of A and B is intended. Further, the recitation of “at least one of A, B, and C” should be interpreted as one or more of a group of elements consisting of A, B, and C, and should not be interpreted as requiring at least one of each of the listed elements A, B, and C, regardless of whether A, B, and C are related as categories or otherwise. Moreover, the recitation of “A, B, and/or C” or “at least one of A, B, or C” should be interpreted as including any singular entity from the listed elements, e.g., A, any subset from the listed elements, e.g., A and B, or the entire list of elements A, B, and C. 

1: A sheet product, comprising: a main body of at least one ply, wherein the at least one ply comprises first fibers comprising a first polymer and second fibers comprising a second polymer or wherein the at least one ply comprises unitary fibers comprising first and second polymers, wherein a cold crystallization temperature of the first polymer is equal to the softening temperature of the second polymer or below the softening temperature of the second polymer. 2: The sheet product of claim 1, wherein the softening temperature and/or the melting temperature of the second polymer is above the softening temperature and/or the melting temperature of the first polymer. 3: The sheet product of claim 1, wherein a difference between the softening temperatures of the first and second polymers as measured to DIN 53765 is at least 15° C. 4: The sheet product of claim 2, wherein a difference between the melting temperatures of the first and second polymers is at least 5° C. 5: The sheet product of claim 1, wherein at least one of the polymers is a polyester selected from the group consisting of polyethylene terephthalate, polypropylene terephthalate, polytetramethylene terephthalate, poly(decamethylene) terephthalate, poly-1,4-cyclohexylene dimethyl terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyglycolic acid, polylactides, polycaprolactones, polyethylene adipates, polyhydroxyalkanoates, polyhydroxybutyrates, poly-3-hydroxybutyrate-co-3-hydroxyvalerates, polytrimethylene terephthalates, vectrans, polyethylene naphthalate, a copolymer of two or more of any of these, or a mixture of two or more of any of these. 6: The sheet product of claim 1, wherein the first polymer has a cold crystallization temperature in a range of from 70 to 150° C. 7: The sheet product of claim 1, wherein the second polymer has a softening temperature in a range from 70 to 150° C. 8: The sheet product of claim 1, wherein at least one fiber comprises the first polymer and the second polymer, and wherein the first polymer is in the form of at least one segment embedded in a second polymer and/or at least partly bordered by the second polymer. 9: The sheet product of claim 8, wherein segments of the first polymer are present in the sheet product in a circular, oval, or n-angular, trilobal, or multilobal cross section, and wherein segments of the first polymer are embedded in the second polymer and/or at least partly bordered by the second polymer. 10: The sheet product of claim 8, wherein the fibers have a sheath-core geometry. 11: The sheet product of claim 1, wherein a weight ratio of the first to the second polymer is in a range of from 50:50 to 95:5. 12: The sheet product of claim 1, wherein the ply is a non-crimp fabric, a woven fabric, a knit fabric, a film, a foil, a batt or a nonwoven. 13: The sheet product of claim 1, wherein the main body includes a composite material comprising the ply. 14: The sheet product of claim 1, having a basis weight as measured to DIN EN 29073 1 in a range of from 50 to 4000 g/m². 15: The sheet product of claim 1, which is a thermoformed sheet product. 16: A bicomponent fiber, comprising: a first polymer; and a second polymer, wherein a cold crystallization temperature of the first polymer is equal to the softening temperature of the second polymer or below the softening temperature of the second polymer. 17: A method for manufacturing a component part of a transport apparatus, the method comprising: a sheet product as claimed in any preceding claim in the manufacture of a component part for a means of transport. 18: The sheet product of claim 1, wherein a difference between the softening temperatures of the first and second polymers as measured to DIN 53765 is at least 20° C. 19: The sheet product of claim 1, wherein a difference between the softening temperatures of the first and second polymers as measured to DIN 53765 is at least 25° C. 20: The sheet product of claim 2, wherein a difference between the melting temperatures of the first and second polymers is at least 10° C. 